1. Field of the Invention
The present invention relates to a decoding apparatus for decoding an encoded image and its control method.
2. Description of the Related Art
Japanese Patent Laid-Open No. 09-186993 discloses a technique for reducing mosquito noise or block noise upon decoding of an encoded image. This technique eliminates noise by segmenting an image into plural areas then adaptively changing filter strength in correspondence with each segmented area.
However, conventionally, the range of filter strength is empirically determined, and it is difficult to quantitatively predict the quality of an image as a worst result of use of the filter strength. Accordingly, in many cases, to avoid image distortion due to noise reduction processing, noise reduction processing with lowered filter strength is performed.